Asia is fighting a new disease that has reduced shrimp output in Thailand as much as 40%, driving prices higher for Western restaurants and retailers.

The disease appeared in Thailand, the world's largest shrimp exporter, late last year after ravaging shrimp stocks in China in 2009 and then in Vietnam. With production plunging, shrimp prices in the U.S. have jumped 20% in recent months, according to Thailand's leading exporter.